Measles epidemics and seroepidemiology of population in Wujin, Changzhou city, Jiangsu province, China 2015

Seroepidemiology of measles in Beijing, China: a cross-sectional study

The aim of this study was to assess the seroprevalence of measles and identify the high risk of measles infection in the general population of Beijing. A total of 2144 subjects aged 0-76 years old were selected using a multi-stage stratified sampling method. Socio-demographic characteristics, vaccination history, and disease history of measles were collected by questionnaire. Serum samples were tested for measles-specific IgG by using commercial ELISA kits. The overall seropositivity rate of measles was 79.80% (95% CI 78.1-81.5%) and standardized seropositivity rate was 84.61% (95% CI 84.12-87.10%), with the median concentration of 773.40IU/L. The area of Beijing with the highest seroprevalence was the central area [81.79% (95% CI 80.16-83.42%) and 855.84IU/L]. There were no significant differences in seropositivity rates of different genders (P = 0.074), history of measles infection (P = 0.421) and registered population (P = 0.598). The 1-4 age group had the highest seropositivity rate [94.06%(95% CI 93.06-95.06%)] and children below the age of 1 (0-12 months) had the lowest seropositivity rate [34.42% (95% CI 32.41-36.43%)]. The 30-34 and 35-39 age groups were relatively lower with 72.90% (95% CI 71.02-74.78%) and 74.65% (95% CI 72.81-76.49%) respectively. Seropositivity rates changed along with the incidence rates of measles periodically by years. As shown in the present study, the seroprevalence of measles antibody in Beijing have not yet met the threshold required to achieve measles elimination and therefore the risk of an epidemic of measles will be existing. Appropriate targeted immunization strategies and measures should be considered and carried out.

Sero-epidemiological study in prediction of the risk groups for measles outbreaks in Vojvodina, Serbia

Background

Age-stratified serologic surveys provide insight into the gaps of measles-specific immunity as well as estimates of the age-specific seroprevalence. The aim of this study was to describe the measles sero-epidemiology in Vojvodina before the occurrence of outbreak in 2017/18 and to discuss preventive measures for potential future epidemics.

Methods

A seroprevalence study was conducted from April 2015 to June 2017 on serum bank of 3199 residual samples. Study was performed prior to the last measles outbreak in Vojvodina that occurred between 12th November 2017 and 30th June 2018. Measles-specific IgG antibodies were determined using an indirect chemiluminescent immunoassay (CLIA).

Results

Median age of enrolled participants was 20 years (IQR 11–37). Overall, 86.9% serum samples were seropositive. The highest proportion of measles seronegativity was observed in children aged 12–23 months of age and in adults aged 20–39 years (56.1% and 18.5%, respectively). Prevalence of measles seronegativity above WHO target levels susceptibility was observed in the following age groups: 2, 7, 13, 15, and among all adults aged between 20 and 49 years. Out of total measles outbreak cases (177), there were 91 (51.4%) participants aged 20–39 years. A significant positive correlation was observed between measles seronegativity and the number of reported measles cases aged ≥ 12 months (r = 0.4675, p = 0.0213).

Conclusions

In order to prevent new outbreaks and achieve the elimination of measles in Vojvodina, the vaccination coverage of both measles-mumps-rubella (MMR1 and MMR2) vaccines needs to be improved and sustained. Educational campaigns for the improvement of acceptance and timely vaccination with vaccine against measles among doctors and the general population are crucial. Our results indicate possible gap in measles protection in adults born during implementation of one dose of measles vaccine and prioritize supplementary immunization activities targeting adults in Vojvodina, Serbia.

Measles vaccination in an increasingly immunized and developed world

Increased measles immunization has led to a significant decline in measles incidence and mortality. During 2016 it is estimated that fewer than 100,000 died from measles for the first time in recorded history. In highly immunized countries measles epidemiology has changed. Threats to national elimination goals and public health include aging cohorts of naïve people that exist from imperfect vaccination rates during the early years of immunization programs. This may be complemented by some loss of immunity in vaccinated populations. While childhood immunization must remain a focus for control efforts, due to higher mortality in the very young, these naïve adolescents and adults also accumulate as they age and add to the pool of susceptible people, perhaps beyond the view of those that are focused on childhood immunization. Here, features of measles epidemiology and control in highly immunized populations are reviewed, providing global data where necessary, to highlight why countries with high immunization coverage are still threatened by measles outbreaks and how changing dynamics may alter disease control.